1. Field of the Invention
The present invention pertains generally to test apparatus. More particularly, the invention relates to portable apparatus capable of simulating a malfunctioning traffic signal controller for checking a system that monitors the operation of traffic signal controllers to determine the operability and response times of the monitoring system.
2. Description of the Prior Art
Pedestrian and vehicular traffic at intersections has, for some time, been controlled by signal lights that are systematically actuated by a central traffic controller. Typically, a source of AC power is switched by load switches operated by the controller in a preprogrammed manner to regulate the orderly flow of traffic through the intersection. The controller effects sequential operation of lights to instruct when to proceed (green or WALK), when to exercise caution (yellow), or when to come to a half (red or DON'T WALK).
Experience has shown that when a traffic controller malfunctions, the least disruption of traffic flow results if the sequencing of the signal lights by the controller is interrupted and the lights caused to flash. A variety of arrangements have been designed to monitor operation of the controller, and to effect transfer of the signal light from a sequencing mode to a flashing mode. Most, if not all, monitoring arrangements operate by monitoring the AC signals that are controlled by the traffic controller to actuate the signal lights. One of the primary functions of a traffic controller monitoring system is to produce a fault indication if two or more permissive but conflicting signal indications are present at the same time. For example, if actuation of one of the green, yellow or WALK signal lights for one direction of a controlled intersection overlaps actuation of one of the green, yellow or WALK signals for an orthogonal direction the monitoring arrangement must be capable of determining whether such overlap is normal or unacceptable; and if determined unacceptable, the monitoring arrangement must be capable of providing a fault indication that can be used by the controller to transfer signal light actuation from the normal preprogrammed mode to a flash mode (e.g., flashing red lights).
In addition, the monitoring system should be able to produce a fault indication when the green, yellow and red signals associated with any one channel are absent for a specified time period. (A channel refers to that group of AC signals sequenced by a controller for actuating the red, green, yellow and WALK signal lights grouped together in one traffic movement). Monitoring systems maintain watch over the AC actuating signals for indications of a faulty load switch, and most are capable of monitoring the 24 VDC from the controller to assure correct operating voltages of the controller, issuing a fault indication when an irregularity is detected.
However, while such monitoring systems, when operating correctly, are available to ensure correct operation of a traffic controller, and to operate to prevent controller malfunction from endangering the public safety, there is presently no known apparatus capable of easily checking the operation and response times of the monitoring system itself.